Galvanometer



Feb. 6, 1945. R A, BORDE 2,368,701

GALVANOMETER Filed July 7, 1943 2 Sheets-Sheet l i f) O w az +97! Feb. 6, 1945. p BORDEN 2,368,701

GALVANOMETER Filed July '7, 1943 -2 Sheets-Sheet 2 ll lllllllll llllllllllllllllllllli ATTO RNEY Patented Feb. 6, 1945 2,368,701 GALVANOMETER Perry A. Borden, Waterbury, Conn.,' asslgnor to i The Bristol Company, Waterbury, Conn., a corporation of Connecticut Application July 7, 1943, Serial No. 493,714

11 Claims.

This invention relates to galvanometers, and more especially to a galvanometer adapted to form a link in an electrical system whereby a small unidirectional potential may be detected and reproduced as an alternating potential adapted to amplification for purposes of measurement or control.

In the determination of small values of electromotive force such as those derived from thermocouples, bridge circuits, pH meters. ammeter shunts, etc. it is customary to apply said E. M. F.s to a circuit including a deflecting galvanometer, and upon the deflection of the moving part of the same to base a function of measurement or control. In many instances the power available from the circuit under measurement is of a magnitude too small to produce a suitable direct deflection on an indicating instrument, and requires a certain degree of amplification. In other cases, where recording or controlling functions are required, still higher amplification is needed. Since small unidirectional potentials are unsuited to direct amplification it is customary to provide a galvanometer of limited defiection and to equip it with some form of relay system actuated thereby and adapted in turn to command the performance of a servomotor or control device whereby the desired final result may be accomplished. This has necessitated fitting the galvanometer with a circuit controlling device or equivalent whereby displacement of the moving part of the instrument might be made to command the relay system. Such devices have heretofore taken the form of contacts adapted to the control of conventional electric circuits, or vanes suited to interposition in the electrostatic or magnetic fields of oscillatory circuits, whereby the flow of current in said circuits is modified. It is obvious that such attachments to the delicate moving element of a galvanometer not only require appreciable forces for their actuation,

galvanometer which, without the addition of mass to the moving element of the instrument, may, by its deflection due to a direct current. control an alternating current suitable for amplification.

It is a further object to provide a device of the above nature in which the phase position and magnitude of the controlled alternating current will vary with the direction and extent respectively of the deflection of the moving element.

It is a further object to provide a device of the above nature in which the current under control shall exert no reaction on the moving element when in its position of maximum sensitivity, and shall exert a substantially negligible efiect when said element is in other positions Within its range of deflection.

but add to the inertia of the movement, and

It is proposed to provide a galvanometer having a movable coil adapted for deflection in a magnetic field wherein there simultaneously exist both a unidirectional and an alternating component. The unidirectional component provides a flux to be reacted upon by direct current flow-- ing in the coil, to produce a deflection of the same; and the alternating component of the field will more or less link with the coil, according to the magnitude of the deflection, whereby there will be induced in said coil an alternating E. M. F. adapted to amplification for purposes oi measurement or automatic control.

Other features of the invention will be hereinafter described and claimed.

In the drawings:

Figs. 1, 2, and 3 are elevations, more or less diagrammatic, of galvanometers embodying the principle of the invention.

Fig. 4 is a diagram showing a galvanometer embodying the principle of the invention in conjunction with electrical circuits suited to theap plication of said principle to the measurement of temperature as determined by a thermocouple,

Fig. 5 is a further alternative form of galvanometer embodying the principle of the invention.

'Fig. 6 is a diagrammatic representation of a form of moving coil alternatively adapted for. use with galvanometers of the class described.

Fig. 7 is a diagram of a self-balancing potentiometer employing a galvanometer of the class described, and adapted to the measurement of temperature as determined by a thermocouple.

A galvanometer incorporating the principle of the invention, is shown in Fig. i, and is described as follows: A coil I0 wound with suitably fineinsulated wire is mounted after the manner oi the conventional dArsonval galvanometers, either on pivots or on suspension ribbons, to encircle a stationary core II, and to be free for deflection through a limited angle about an axis l2 passing through said core. Connection between the winding of the coil III and outside circuits is provided by suitable leads l3 and. il including flexible elements, which may be one or more springs l5, and leading to stationary terminai l3 and I1. A field structure comprises a pair of polar projections l3 and I9 juxtaposed to the edges of the coil l and forming air gaps with the core il, a permanent magnet element 20, and yokes 2i and 22, whereby the magnetic circuit including the permanent magnet is made complete, with exception of the air gap in which the coil III is free to deflect. The polar projections l3 and I3 and the yokes 2i and 23 may be formed of suitable term-magnetic material, and the permanent magnet 20 may effectively be formed or one or other of the highcoercive-iorce steels suited to the construction oi magnetic elements having a high degree of etflciency. The galvanometer, as thus far described, diflers in no patentable details from the conventional permanent-magnet, moving-coil unit; and for it no invention is herein claimed.

Wound upon the polar projections i3 and is are coils 23. and 24 interconnected, to have additive polarity, whereby current flowing therein will tend to produce a flux through the magnetic circuit following substantially an identical path to the flux developed by the permanent magnet 20. The coils 23 and 24 are adapted for excitation from an A. C. source 25, whereby an alternating magnetic flux will be superimposed on the unidirectional flux produced in the magnetic circult by the permanent magnet 20. It will be observed that, with the coil ill in the position shown in Fig. 1, with the plane oi. the winding parallel to the general direction of the fiux in the air gaps and none of the flux linking with the coil (this being the position of zero mutual inductance between the movable coil and the field) not onlywill it be impossible for the alternating component of the flux to induce any electromotive force in said coil, but the coil will have maximum sensitivity for deflection due to the reaction of any unidirectional component of current fiowing therein upon the corresponding component of the magnetic field. It direct current is caused to flow in said coil, causing it to be angularly deflected from said position of zero mutual inductance, said deflection will cause the coil to link with more orless of said flux, according to the extent of the deflection, whereby the alternating component of the flux will cause an alternating electromotive force to be induced in the coil, and the magnitude of said E. M. F. will vary with the extent of deflection oi the coil from said zero position, while the phase position, or instantaneous polarity 01 said E. M. F. with respect to that of the exciting current flowing in the windings on the polarprojections, will depend upon the direction of said deflection.

In Fig. 2 is shown an arrangement alternative to that shown in Fig. 1, whereby a galvanometer may be provided with a field having both unidirectional and alternating components to accomplish the purposes of the invention. A movable coil 30 encircles a core 3| positioned between polar projections 32-33 of an electromagnet structure including a portion 34 adapted to receive a winding, and yokes 35 and 33, whereby there is provided a magnetic circuit complete with exception of the air gaps between the polar projections and the core 33, in which gaps the active conductors of the coil 30 are free for deflection. The magnetic system is formed of fer romagnetic material, and may be oi laminated construction if rendered necessary by the altergating component of the fiux to be carried there- Wound upon the portion 34 are windings 31 and 33 adapted for energization from a D. C. source 39 and an A. C. source 30 respectively. Adjustable rheostats 4i and 42 in the circuits between said windings and aid sources, provide for regulation oi. the values of direct current and alternating current respectively in said windings, with a corresponding adjustment in the values of the consequent components of the flux in the magnetic circuit. Connection between the movable coil 33 and external circuits is provided by suitable flexible conductors leading to stationary terminals 43 and 4|.

The operation of the galvanometer shown in Fig. 2 is similar to that shown in Fig. l, the only difference lying in the fact that the unidirectional component or the field is derived from an electromagnetic source instead of from a permanent magnet. With the coil 30 in the position of zero mutual inductance as shown, there will be obtained maximum sensitivity of response to the flow of direct current in the coil 30, and at the same time a zero value of linkage with the field, and consequently no induced alternating E. M. F. in the coil. As the coil 33 becomes angularly deflected it will link with the flux; and, as hereinabove set forth in the explanation of the rorm of the invention shown in Fig. 1, have induced in it an alternating E. M. F., which may be transformed, amplified, or subjected to any of the forms of detection or measurement to which alternating potentials are especially adapted.

In Fig. 3 is shown an alternative form of galvanometer embodying the principle of the invention, and having a single field winding adapted. to carry a current having both unidirectional and alternating components, whereby corresponding fluxes may simultaneously be caused to fiow in the magnetic circuit. A movable coil 53, encircling a core BI, and adapted to deflect within an air gap formed between polar projections 5! and 53 and said core, provides a sensi tive element identical in all respects with the corresponding parts shown in Fig. 2. Connection between the movable coil 50 and external circuits is provided by suitable flexible conductors leading to stationary terminals 54 and 55. The magnetic circuit is completed by a winding portion 56 and yokes 51 and 53 providing a path for flux passing through said air gaps. The portion 53 is provided with a single winding 59 adapted to carry magnetizing current.

A mixture of direct and alternating current, or a current having both unidirectional and alter nating components, may be obtained from any one of a number of well known circuits. One form of such a source is shown in Fig. 3. A full-wave dry-type rectifier bridge 60 is con-- nected to an A. C. source 3i and to the winding 59 in such a manner that rectified current from said source will pass through said winding, producing a unidirectional magnetomotive force in the magnetic circuit. Shunted across two opposite arms or the bridge 83 are adjustable resistors 82 and 33, which provide a path permitting a non-rectified component of current to flow between the two sides of the source 6| through the winding 59 and the resistors 62 and 69 in series, whereby the magnitude of said component will be made subject to the settings of said resistors There is thus provided in the winding 69 an exciting current having superimposed unidirectional and alternating components, whereby there will be produced in the air-gaps of the galvanometer a corresponding field suited to the purposes of the invention, as hereinabove set forth.

In Fig. 4 is shown a galvanometer structurally similar to that shown in Fig. 3, but with an alternative type of circuit for supplying a suitable magnetic field, and also with a type of circuit whereby the galvanometer may perform its function of a conversion instrument. A movable coil 61 encircling a core 68 and adapted to be angularly deflected about an axis 69 and within an air gap formed between polar projections 10 and 1| and said core, is suitably and flexibly connected to stationary terminals 12 and '13, and provides a sensitive element identical in all respects with the corresponding element shown in Fig. 3. The magnetic circuit is completed by a winding portion 14 and yokes 15 and 16. The portion 14 is provided with a winding 11 adapted to carry magnetizing current derived simultaneously from a D. C. source 18 and an A. C. source 19. One side of the magnetizing winding "is connected to one side of each of said sources by means of a conductor 80. The free side of the winding 11 is connected to the free sides of both of said sources through a filter system 8i, and adjustable rheostat 82 and 83 in series with the D. C. and A. C. sources respectively, whereby the respective and relative values of the unidirectional and alternating components of the magnetic flux may be varied at will. The filter system 8! includes a capacitor 84 adapted to pass alternating current only, while blocking the flow of direct current, and an inductance 85 adapted to permit the flow therethrough of direct current, while assing a negligible proportion of alternating current. The capacitor 84 is connected in series with the circuit through which current is derived from the A. C. source 19, and the inductance 85 in series with the circult through which current is derived from the D. C. source 18. The fil er system as here described is elementary, and is based on a principle well known to those familiar with electrical networks; and, as it forms no essential part of the present invention, need not here be described in further refinement or detail.

In Fig. 4 is shown also a circuit whereby the principles of the galvanometer embodying the invention may effectively be utilized. A thermocouple 86, exposed to a temperature to be measured, has one of its elements electrically connected to the terminal 12, ing connected to the terminal 13 in series with the primary winding of a coupling transformer 81 forming a part of an amplifying system 88. Included in the amplifying system 88 is a triode 89 of the conventional type having a filament 99, a grid 9| and a plate 92. The filament 90 is included in circuit with a battery 93, whereby electrons may be emitted therefrom. The plate 92 is included in circuit with the primary winding of a transformer 94 and with a battery 95 of relatively high potential suitably connected to the circuit of the filament '90, whereby said filament and plate constitute the cathode and anthe other element beode respectively of an electronic circuit through the triode 99 and the primary winding to the transformer 94. The secondary winding of the transformer. 94 is connected to the terminals of an electrical instrument 96 adapted to measure the alternating voltage-induced in said winding and thus the A. C. component of the current in the plate circuit of the triode 99. The grid 9| is included in circuit with a battery 91 and the secondary winding of transformer 61, the potential of said battery being so selected or adjusted that the potential between the grid 9| and the filament 99 will be varied by alternating potential derived from the secondary winding of the transformer 91, and will thus cause to flow through the circuit of the plate 92 a current having an alternating component dependent in all characteristics upon said alternating potential, which component, acting through the transformer 94 will be quantitatively determined by the instrument 96.

The action of the combination shown in Fig. 4 is as follows: The magnetizing winding 11 being excited by current from both sources 18 and 19, and therefore having both a unidirectional and an alternating component, the magnetic flux in the air gaps will have corresponding superimposed components; and by means of the rheostats 82 and 83 the actual and relative magnitudes of these components may be regulated at will. The galvanometer will first be adjusted so that with no current flowing in its moving coil said coil will lie in its position of mutual inductance. Assuming first a condition in which all parts of the thermoelectric circuit are at a comrnon temperature, and consequently no electromotive force is being developed in the circuit including the thermocouple 86 and said coil there will be no current flowing therein, and the coil will lie in said adjusted position, where, as hereinbefore pointed out, there being no linkage between the winding of said coil and the flux in the magnetic system, no potential can be induced in the former. The amplifier system Bil will then operate in its normal state; and the reading of the nstrument 96 may be designated as representing the temperature of the thermoelectric c1rcu1t. Assuming now a change in the temperature to which thethermocouple is exposed, the thermoelectromotive force SQ developed will cause a unidirectional current to pass through the circult including the galvanometer coil 61, reacting upon the unidirectional component of the flux 1n the air gap, with a consequent tendency of the coil 61 to deflect about the axis to an angular position as indicated i Fig. 4, and to an extent depending upon the magnitude of said current. the coil 61 is angularly deflected about ts axis it will assume a positionwherein linkage is established with the flux in the air gap of the magnetic circuit; and the alternating component of said flux will cause to be induced in said coil an E. M. F. depending in magnitude upo the extent of the angular deflection of the coil 61 from its normal position of zero mutual inductance with the field. The E. M. F. developed in the 001161 is applied through the transformer 81 (which blocks the flow of direct current fromthe thermocouple circuit into the electron tube system) to the amplifier circuit, by which it is suitably amplified, causing to flow in the plate c1rcu1t and the instrument 96 a current whose magnitude as indicated on the scale of said in strument becomes a measure of the temperature to which the couple 96 is exposed.

By selecting suitable characteristics for the amplifying circuit the alternating component of current in the galvanometer moving coil necessary to provide a suitably amplified output may be established at a magnitude and phase position wherein the reaction between said component and the corresponding component of the magnetic fleld will be negligible in positions of extreme deflection of said coil. Moreover, as previously pointed out, in the position of maximum sensitivity to unidirectional current flow, since no alternating component is induced in that coil, the reaction between the same and the alternating component of the field can have none other than a zero value.

In Fig. 5 is shown a galvanometer embodying the principle of the invention, and having a magnetic circuit differing from those heretofore set forth, in that while the unidirectional component or the magnetic field is provided by a permanent magnet structure, the principal alternating component of said fleld is not required to traverse the permanent magnet material. A movable coil III encircling a core I02 and adapted to be angularly deflected about an axis I03 is Provided with suitable flexible connections to stationary terminals I04, I00, whereby connection maybe made to an external circuit. Juxtaposed to the edges of the core I02 and forming therewith air gaps in which the coil IOI may deflect are polar structures I00 and I01. Unidirectional flux in the air gaps is provided by permanent magnets I06 and I01, which may be formed of alnico or other highcoercive force material, whereby the magnets will have a short stocky conformation, together with a bridge-piece I00, serving to complete a magnetic circuit, with exception of the air gaps adjacent the polar structures I00 and M1. Said Polar structures are provided with winding portions I00 and H0 respectively, approaching one another in a sense to shunt the core I02 and associated air gaps, but in themselves separated by an air gap II I of length comparable with that of the air-gap portion of the magnetic circuit in which the coil MI is positioned. Wound upon the portions I00 and H0 respectively are coils H2 and H3, interconnected to form the equivalent of a single solenoid, and adapted to be energized from an A. C. source H4. The core I02, and the polar structures, as well as the bridge-piece I00 are preferably formed 01' ferro-magnetic material.

Under operating conditions, the permanent magnets I00 and I01 will provide a flux of which a part will traverse the core I02 and associated air gaps and a part will traverse the winding portions I09 and H0 and the air gap III. By suitable selection of the relative lengths of the air gaps in the two branches of the magnetic circuit, the proportionality of distribution of the flux between said branches may be controlled. Upon II4 through the interconnected coils I I2 and H3, the component of flux. passing through the branch or the magnetic circuit upon which said coils are wound will be alternately opposed and reinforced. so that flux will be alternately shunted into, and diverted from, that branch 'of the magnetic circuit in whose air gaps is located the movable coil m. said coil m is thus provided with a field haying bbth a unidirectional and an alternating component; and by suitable design of the mag netic circuit the part of the alternating component traversing the permanent magnets I00 and Ill may be reduced to negligible proportion.

the passage of alternating current from the source The operation of the galvanorneter shown in Fig. 5 is in all respects identical with that set forth in connection with the hereinbefore described forms having a combined unidirectional and alternating field, and need not be explained i further detail.

In Fig. 6 is shown a form of movable coil with which it may at times be found expedient to provide a galvanometer embodying the principle of the invention. On a form II9 adapted for angular deflection about an axis I20, and surrounding a core I2I positioned between pole pieces I22 and I23, is placed a winding having two electrically independent sections I24 and I25. While these are shown as wound in opposite directions about the form I I9, and also as having a common connection, it will be obvious that they may be wound in the same direction if desired. Furthermore, it will be apparent that interconnection is not essential, and that by providing an additiona1 flexible lead the two windings may be entirely isolated from each other. There are a number of types of installation where such an arrangement as that shown in Fig. 6 may be expediently used. Among these may be mentioned the following: (a) where it is necessary that the D. C. and A. C. circuits be mutually isolated, (b) where complete isolation may not be necessary, but it is desired to eliminate alternating potential in the D. C. circuit and/or vice versa, (0) where the relative magnitudes of the respective components of the field flux with respect to those of the E. M. F.s in the two circuits, make it desirable that diiferent numbers of turns be used in the two windings. While for purposes of clarity in a representation, the two windings in Fig. 6 have been shown as occupying diilerent portions of the winding face of the form I I9, actual construction would generally call for these windings to be distributed, and interleaved to occupy as nearly as possible a common electrical position in space.

In Fig. '7 is shown the application of a galvanometer embodying the principle of the invention to use in a potentiometer of the self-balancing class for the measurement of temperature as determined by a thermocouple. Mounted upon, but insulated from, a base I30 is a slide wire I3I, adapted to be supplied with current from a battery I32 through an adjustable rheostat I33. whereby a predetermined potential gradient may be maintained over the extent of the slide-wire.

Cooperating with the slide-wire I3I is a sliding contact I34 mounted upon a carriage I35 and thus adapted to be positioned at any point along the extent of the slide-wire by means of a lead screw I 30 which may be driven in either direction through a gear train I31 operated by a reversible motor I38.

The motor I38 is provided with a field winding I39 adapted for excitation from an A. C. source, and an armature winding I40 also adapted to be energized by alternating current; and the direction and speed of rotation of the shaft of the motor are governed by the relative instantaneous polarities and the intensities of the respective current in said windings. The windin I39 is continuously excited from an A. C. source I4I, so that complete control of operation of the motor is obtained by suitable regulation of the characteristics of the current flowing in the winding I40. An index or pointer I42 mounted upon the carriage I35 cooperates with a graduated scale I43 to provide a measure of the excursion of the contact I34 along the slide-wire I3I from a predetermined Point of reference.

Mounted upon the base I is a galvanometer I44, which may be of any one of the several forms hereinbefore set forth (for example, the form shown in Fig. 1, having the unidirectional com nent of its field flux provided by permanent agnet means and the alternating component of said flux from an A. C. source) with its A. C. exciting winding connected to the source I and having a movable coil I45 adapted for angulardeflection in the composite field provided by the superimposed influences of said unidirectional and alternating means of excitation. Also mounted upon the base I30 is an amplifier I46 similar to the amplifier 88 shown in Fig. 4 and having input terminals I41 adapted to have applied thereto an alternating current for amplification, and output terminals I48 connected by means of conductors I49 to the winding I of the motor I38, whereby there may be supplied to said winding an alternating current dependent in magnitude and phase position upon the characteristics of the E. M. F. applied to the terminals I41. A thermocouple I49, exposed to a temperature to be measured,has one of its elements connected to an extremity of the slidewire I3I, and its other element to one side 01' the moving coil I in the galvanometer I44. The other side of said moving coil is connected tothe sliding contact I34 in series with the input terminals I41 of the amplifier I40, whereby E. M. F. developed in said galvanometer coil'will be amplified and impressed upon the winding I40 of the motor I38.

The operation of the instrument shown in Fig. 7 is as follows: Assuming first a condition of balance between the E. M. F. developed by the thermocouple I49 and that existing across the portion of the slide-wire I3I to which said E. M. F. is applied through the galvanometer moving coil and the contact I34, there will be no flow of current in the circuit so defined, and the moving element of the galvanometer will rest in its neutral position, in which position, as hereinbefore pointed out, there will be no linkage between the coil I45 and the flux existing in the air gap of the magnetic system. Consequently the alternating component of said flux will induce no potential in said coil, and no voltage will be impressed by the amplifier I45 upon the wind ing I40 of the motor I38, so that the motor will remain at rest, no movement of any part of the instrument taking place so long as the aforesaid condition of balance is maintained, and that the position of the pointer I42 with respect to the scale I43 may be taken as a measure of the temperature to which the thermocouple I49 is exposed.

Assuming now achange in the potential developed by the thermocouple, due to a variation in the temperature measured, there will no longer exist a condition of balance to the couple circuit, with the result that a unidirectionalcurrent will flow in the same, including the coil I45. reacting upon the unidirectional component of the flux in the air gap, with a consequent tendency of said coil to deflect angularly about its axis, as indicated in the drawing, in a direction dependent upon the sense of the change in thermo-electromotive force, and to an extent deendent upon the magnitude of said change. As thecoil I45 is angularly deflected about its axis, it will assume a position wherein linkage is established with the flux in the air gap of the magnetic circuit; and the alternating component 0! said flux will cause to be induced in said coil an E. M. F. depending in polarity with respect to the A. C. excitation of the winding of the galvanometer upon the sense 01' said deflection, and in magnitude upon the extent of the same. The E. M. F. developed in the coil I45 is applied to the input terminals I41 01. the amplifier I46, wherebyv an amplified E. M. F. having its intensity and phase position subject to the deflection of the galvanometer coil is impressed upon the armature winding I40 01 the motor I38. The motor I38 will thus be caused to operate; and since the phase position and intensity or the current flowing in its armature winding I 40 and adapted to react upon the current flowing in the field winding I39, are dependent upon the deflection of the galvanometer'coil I45, the direction and speed of'travel of the carriage I35 bearing the contact I34 will depend upon the degree or unbalance in the thermocouple circuit. Polarities and relative magnitudes of currents and potentials in the several circuits being suitably selected and adjusted, there is thus provided a self-balancing potentiometer adapted to the quantitative and continuous determination of temperature values as detected by the thermocouple I49 and indicated by the pointer or index I42 upon the graduated scale I43.

It will be apparent that, if desired, the potentiometer may effect recording and controlling, in addition to indicating variable values. For instance, there may be employed, in conjunction with said potentiometer, recording and controlling mechanisms such as are illustrated in the Hunt Patent No. 2,082,109, issued June 1, 1937.

The terms and expressions which I have employed are used as terms of description and not of limitation, and I have no intention, in the use of such terms and expressions, of excluding any equivalents of the features shown and described or portions thereof, but recognize that various modifications are possible within the scope of the invention claimed. It will be understood that the term 0011" or winding as employed in the ensuing claims includes within its scope a coil or winding arrangement, such as illustrated in Fig. 6, comprising electrically independent sections for D. C. and A. C. currents, respectively, which sections are movable concurrently within an air gap having a magnetic field comprising both unidirectional and alternating components.

I claim:

1. In a galvanometer for responding to a unidirectional current, a magnetizable structure having an air gap, a coil adapted to carry said current and movable in said gap, means for producing in said structure and in said gap a unidirectional magnetic field, means for superimposing an alternating component upon said field, and means connected with said coil and responsive to alternating E. M. F. induced therein.

2. In a galvanometer for responding to a unidirectional current, a magnetizable structure having an air gap, a coil adapted to carry said current and movable in said gap, means for producing in said structure and in said gap a unidirectional magnetic field, means for causing the strength of said field to vary periodically through a predetermined cycle of intensity, and means connected with said coil and responding to alternating E. M. F. induced therein.

3. An electric instrument having a magnetizable structure including a gap, a defiectable winding having conductors adapted for limited movement in saidgap. means tor exciting said responding component of said fleld to deflect structure to produce a unidirectional magnetic said winding, and means responsive to alternatmm i said ga means for exciting said strucing E. M. F. induced by said alternating comtur to produce a superimposed alternating magponent in said winding when deflected. netic neidinsaid gap. means for impressing upon 8. Electrical apparatus for responding to a said winding an electromotive force to be deunidirectional current, said apparatus comprist t d, and measuring means responsive to aling a structure providing an air gap, a coil ternating eiectromotive force induced in said adapted to carry said current and movable in v said gap, means for producing in said gap a 4. In an electric instrument, a magnetizable magnetic field having unidirectional and altermmrs, means for producing in said structure nating components, and means connected to said a magnetic fleld having superimposed a unicoil and responsive to alternating E. M. F. indirectional component and an alternating comduced therein for measuring said E. M. F. ponent, said superimposed components being 9. A galvanometer comprising a deflectable geometrically coincident, a deflectable winding winding, a field structure providing an air gap having conductors movable in said field. means wherein said winding may be deflected and may tor impressing upon said winding a unidirecinductively coact with a magnetic field, means ticnal E. M. I". to produce a current adapted to for providing in said gap a magnetic field comreact with said fleld to deflect said winding, and prising unidirectional and alternating commeasuring means responsive to alternating elecgo ponents, and means for regulating the relative tromotive i'orce induced in said winding. v strengths of said components whereby to modiiy 5. In an electric instrument, a magnetizable the relative intensities of the inductive coaction structure, means for producing in said structure between said winding and the respective com.- a magnetic fleld having a unidirectional components of said field. ponent and an alternating component. said 10. A galvanometer comprising a structure components being geometrically coincident, a deproviding an air gap, a deflectable winding movilectable inductive winding having conductors able in said gap, means for providing in said gap movable in said field and normally occupying a a magnetic field comprising unidirectional and position of zero mutual inductance with the alternating components, means for impressing some, means for passing through said conductors upon said winding a unidirectional E. M. F. to a unidirectional current to react with the correproduce a current adapted to react with the corsponding component of said fleld to deflect said responding component of said field to deflect winding away from said position of zero mutual said winding, means responsive to alternating inductance, and means responsive to alternating E. M. F. induced by said alternating component electromotive force induced by said alternating as in said winding when deflected, and means for componentinsaid winding when deflected. regulating the relative strengths of said unie. In an electric instrument for responding to directional and alternating components oi said a unidirectional current, the combination of an magnetic field whereby to modify the relative inelement angularly deflectable about an axis, said tensities of the inductive coaction between said element including conductor means having a 4.0 winding and the respective components of said directional component substantially parallel to field. said axis and movable in a sense substantially 11. A galvanometer comprising a structure perpendicular thereto. means to provide a magproviding an air gap, a deflectable winding movnetic fleld having superimposed unidirectional able in said gap, means for providing in said and alternating components, means for causing 5 gap a magnetic field comprising unidirectional said components to follow a common path havand alternating components, means for impress- 8 a directional component substantially pering upon said winding a unidirectional E. M. l". pendicular both to said conductor means and to to produce a current adapted to react with the the motion oi the same, means providing a path corresponding component 01' said field to deior said unidirectional current and including said fiect said winding, measuring means responsive conductor means, and further means coupled to to alternating E. M. F. induced by said alternatsaid conductor means and sensitive to electroing component in said winding when deflected, motive force inducedin the same. and means for regulating the relative strengths 7. Electrical apparatus comprising a structure of said unidirectional and alternating comproviding an air gap, a deflectable winding mov- BI ponents of said magnetic field whereby to modify able in said gap, means for providing in said gap the relative intensities of the inductive coaction a magnetic fleld comprising unidirectional and between said winding and the respective comalternating components, means tor impressing ponents of said field. upon said winding a unidirectional E. M. 1'. to PERRY A. BORDER. produce a current adapted to react with the corso DISCLAIMER 2,368,701.Perry A. Borden, Water-b Conn. Gsnvsnoun'rnn. Patent dated Feb. 6, 1945. Disclaimer filed ar. 18, 1947, by the assignee, The Bristol Company. Hereby enters this disclaimer to claims 1,2, 3, 4, 5, 6, 7, 8, and 9 of said patent;

[Qficia Gazette April 16, 1.9471] 

